1. Field of the Invention
This invention relates to programmable timing circuits, and, in particular, to non-linear programmable timing circuits. Accordingly, it is a general object of this invention to provide new and improved circuits of such character.
A programmable timing circuit, in accordance with this invention, can generate a precise timing interval which can be conveniently adjusted by a potentiometer. It finds general applications in the fields of machine control and materials handling, particularly in combination with other devices to form a time delay relay.
2. Description of the Prior Art
Programmable time delays employing electronics generally fall into two categories, an RC analog technique employing a potentiometer or a digital technique which usually employs multiposition discrete switches.
The RC technique, generally, relies upon the time interval created by the charging of a capacitor through a resistor. Disadvantageously, a problem arises in generating long delays, in that, for long delays, the charging currents are very small, and capacitor leakages are so high that reliable and repeatable performances over time and temperature become a complex task.
The digital technique, generally, relies upon a high frequency clock source which is frequency divided, and time is selected by digital switching. However, the cost and size of a suitable digital switch mechanism makes such an apparatus impractical for many applications.